Arthromelodes lotus, Yin, 2022

Yin, Zi-Wei, 2022, The Batrisini of Tibet: unveiling an enigmatic ant-loving beetle diversity at Earth’s “ Third Pole ” (Coleoptera, Staphylinidae, Pselaphinae), Zootaxa 5111 (1), pp. 1-211 : 47-49

Arthromelodes lotus sp. nov.

( Figs 19 , 78C , 99F )

Chinese common name: Ṑ+njà甲

Type material ( 1 ex.). HOLOTYPE: CHINA: ♂, ‘ China: Xizang, Mêdog County, Renqingbeng Temple (ca. 29°18’45”N, 95°21’27”E), 1760–2200 m, 19.iii.2017, Wen-Xuan Bi leg., [ƱẪẸṘ仁ů崩寺]’ ( SNUC).

Diagnosis. Male. Body length approximately 1.8 mm. Head subtruncate at base; vertexal foveae large and asetose, lacking sulcus connecting them; antenna elongate; antennomeres slightly elongate, lacking modifications. Discal stria of elytron extending posteriorly to approximately apical 1/3 of elytral length. Mesotrochanter with small ventral spine, mesotibia with triangular apical spur. Tergite 1 (IV) heavily modified, with large central cavity and projections inside. Aedeagus strongly asymmetric; median lobe with large basal capsule and rounded triangular foramen, ventral stalk dilated at apex; dorsal lobe broad at middle, narrowing towards base and apex.

Description. Male. Body ( Fig. 19A ) length 1.78 mm; color dark reddish-brown, antennae, tibiae, tarsi and mouthparts yellowish-red. Dorsal surface of body covered with scattered long pubescence and normal ones.

Head ( Fig. 19B ) subtruncate at base, slightly wider than long, length 0.37 mm, width across eyes 0.42 mm; vertex finely punctate, with large, asetose vertexal foveae (dorsal tentorial pits), lacking U-shaped sulcus connecting foveae, mediobasal carina extending from head base anteriorly to transverse sulcus between antennal tubercles, post ocular areas and frons coarsely punctate; antennal tubercles moderately raised; frons slightly impressed medially, confluent with clypeus; clypeus with scattered large punctures, its anterior margin carinate and moderately raised; ocular-mandibular carina complete, carina branched below eye, extended ventrally and then anteriorly to posteroventral articulation of mandible. Venter with gular foveae (posterior tentorial pits) fused in single oval opening, with distinct median carina extending from middle anteriorly to mouthparts. Eyes moderately prominent, composed of approximately 19 large ommatidia. Antenna moderately elongate, length 0.94 mm, simple, club loosely formed by moderately enlarged apical three antennomeres; antennomere 1 thick, subcylindrical, 2–8 each slightly elongate, 3 and 8 smallest, 9 much larger than 8, 10 as long and as wide as 9, 11 largest, longer than 9 and 10 combined, subconical.

Pronotum ( Fig. 19B ) approximately as long as broad, length and width 0.44 mm, widest at middle; lateral margins rounded, with few exceptionally long setae; disc slightly convex, finely punctate, median longitudinal sulcus as long as semicircular lateral sulci in dorsal view, the latter extending from dorsal surface laterally and posteriorly and then fusing with lateral ends of antebasal sulcus; lacking median antebasal fovea or mediobasal carina, lateral antebasal foveae connected by transverse antebasal sulcus; outer and inner pair of basolateral foveae distinct. Prosternum with anterior part as long as coxal part, with small lateral procoxal foveae; hypomeral ridge extending from base anteriorly towards half of apical part, with lateral antebasal hypomeral impression; margin of coxal cavity weakly carinate.

Elytra much wider than long, length 0.50 mm, width 0.61 mm; each elytron with two large, asetose basal foveae, lacking subbasal fovea; discal stria extending from outer basal fovea to approximately apical 3/5 of elytral length; humerus weakly prominent, with small subhumeral fovea, sulcate marginal stria extending from fovea to posterior margin of elytron.

Mesoventrite short, demarcated from metaventrite by ridged anterior edges of impressed areas where lateral mesocoxal foveae situated at mesal margins, with pair of thin admesal carinae; setose median mesoventral foveae widely separated, lateral mesoventral foveae large and setose, broadly forked internally; intercoxal process short. Metaventrite broadly impressed at middle, admesal areas weakly prominent; with large, setose lateral mesocoxal foveae and pair of smaller, setose lateral metaventral foveae, posterior margin with small and narrow split at middle.

Legs moderately elongate; protrochanter with tiny ventral spine; mesotrochanter ( Fig. 19C ) with small, acute spine on ventral margin, mesotibia ( Fig. 19D ) with distinct triangular apical spur.

Abdomen widest at lateral margins of tergite 1 (IV), length 0.51 mm, width 0.56 mm. Tergite 1 (IV) ( Fig. 19E ) in dorsal view longer than tergites 2–4 (V–VII) combined, setose basal sulcus separated by mediobasal and one pair of basolateral foveae, with pair of relatively long discal carinae, large central cavity occupying most surface of tergite, inside with large tubercles at apex of and two small laminae at posterolateral margins of cavity, with broad longitudinal sulcus lateral to each side of cavity; tergites 2 and 3 (V and VI) lacking foveae, 4 (VII) as long as 2 and 3 combined along middle, with one pair of basolateral foveae, tergite 5 (VIII) semicircular, posterior margin roundly emarginate at middle. Sternite 2 (IV) with large mediobasal and broad basolateral sockets, with pair of long, thick lateral carinae; midlength of sternite 2 (IV) as long as sternites 3–5 (V–VII) combined, 3 and 4 short, 5 slightly longer than 4, 3–5 lacking foveae, sternite 6 (VIII) transverse, posterior margin emarginate at middle, sternite 7 (IX) ( Fig. 19F ) slightly oval, moderately sclerotized, apex rounded and with few long setae along apical margin.

Aedeagus ( Fig. 19G, H ) 0.30 mm long, strongly asymmetric; median lobe with large basal capsule and rounded triangular foramen, ventral stalk dilated at apex and with pointed expansion before apex; dorsal lobe elongate, broadest near middle, narrowing towards base and apex; parameres reduced to single broad membranous structure.

Female. Unknown.

Comparative notes. The new species resembles A. flosculus by the presence of exceptionally long setae along the posterolateral margin of the head, lateral margin of the pronotum, and elytral disc. Arthromelodes lotus can be readily separated from A. flosculus by the much smaller body size (1.78 mm vs. 2.62 mm), the more robust antennae, the presence of a large apical spur of the mesotibiae, and a different structure and form of the abdominal modification and the aedeagus.

Distribution. Mêdog County, Tibet, SW China ( Figs 78C , 99F ).

Etymology. The specific epithet is a Latin adjective meaning ‘washed, bathed’, referring to Mêdog (Pemako) being regarded as the ‘Lotus Holy Land’ to the Tibetan Buddhists.

Figures

FIGURE 19. Morphology of Arthromelodes lotus sp. nov., male. A. Dorsal habitus. B. Head and pronotum. C. Mesotrochanter. D. Apical part of mesotibia. E. Tergite 1 (IV). F. Sternite 7 (IX). G, H. Aedeagus, lateral (G) and ventral (H). Scale bars: 0.5 mm in A; 0.3 mm in B; 0.1 mm in C, D, G, H; 0.2 mm in E; 0.05 mm in F.

FIGURE 78. Distribution of Tibetan Batrisini. A. Arthromelodes cylindricus sp. nov. (circle), A. flosculus sp. nov. (triangle) and A. gyamda sp. nov. (square). B. A. intricatus sp. nov. (circle), A. lage sp. nov. (triangle) and A. langjicuo sp. nov. (square). C. A. latithorax sp. nov. (circle), A. lebus sp. nov. (triangle) and A. lotus sp. nov. (square).

FIGURE 99. Environment of and collecting sites at Nyingchi area. A. Beibeng Township (Ü崩乡). B. Road near Gelin Village (格ff村). C. A bridge at Yarang (亚ü). D. A village near Guoguotang Great Bend (果果Ƌkm弯). E. Environment near Mêdog County (ẸṘ县). F. Path to Renqingbeng Temple (仁ů崩寺). G. An overall view of Guoguotang Great Bend. Photo Credit: E, F by Xiao-Bin Song.